Move css style related to scwidgets.css_style level (#103)

The css style related functions are not essential for creating a
exercise notebook so we move it one level higher. For that we rename the
`_css_style.py` to `css_style.py`.

src/scwidgets/__init__.py

@@ -1,16 +1,12 @@
 __version__ = "0.1.0-dev0"
 __authors__ = "the scicode-widgets developer team"
 
-from ._css_style import CssStyle, get_css_style
 from .check import *  # noqa: F403
 from .code import *  # noqa: F403
 from .cue import *  # noqa: F403
 from .exercise import *  # noqa: F403
 
 __all__ = [  # noqa: F405
-    # css_style
-    "CssStyle",
-    "get_css_style",
     # cue
     "CueWidget",
     "CheckCueBox",

src/scwidgets/check/_widget_check_registry.py

@@ -7,8 +7,8 @@
 
 from ipywidgets import Button, HBox, Layout, Output, VBox, Widget
 
-from .._css_style import CssStyle
 from .._utils import Formatter
+from ..css_style import CssStyle
 from ._check import Check, CheckResult
 
 

src/scwidgets/exercise/_widget_code_exercise.py

@@ -12,11 +12,11 @@
 from widget_code_input import WidgetCodeInput
 from widget_code_input.utils import CodeValidationError
 
-from .._css_style import CssStyle
 from .._utils import Formatter
 from ..check import Check, CheckableWidget, CheckRegistry, CheckResult
 from ..code._widget_code_input import CodeInput
 from ..code._widget_parameter_panel import ParameterPanel
+from ..css_style import CssStyle
 from ..cue import (
     CheckCueBox,
     CheckResetCueButton,

src/scwidgets/exercise/_widget_exercise_registry.py

@@ -11,8 +11,8 @@
 from IPython.display import display
 from ipywidgets import Button, Dropdown, HBox, Label, Layout, Output, Text, VBox
 
-from .._css_style import CssStyle
 from .._utils import Formatter
+from ..css_style import CssStyle
 
 
 class ExerciseWidget:

src/scwidgets/exercise/_widget_text_exercise.py

@@ -2,8 +2,8 @@
 
 from ipywidgets import HTML, HBox, HTMLMath, Layout, Output, Textarea, VBox
 
-from .._css_style import CssStyle
 from .._utils import Formatter
+from ..css_style import CssStyle
 from ..cue import SaveCueBox, SaveResetCueButton
 from ._widget_exercise_registry import ExerciseRegistry, ExerciseWidget
 

tests/notebooks/widgets_cue.py

@@ -16,10 +16,10 @@
 # +
 from ipywidgets import Text, VBox
 
-import scwidgets
+from scwidgets.css_style import get_css_style
 from scwidgets.cue import CheckCueBox, CueBox, ResetCueButton, SaveCueBox, UpdateCueBox
 
-scwidgets.get_css_style()
+get_css_style()
 # -
 
 # Test 1: